Particle beam irradiation method and particle beam irradiation apparatus used for the same

ABSTRACT

In a particle beam irradiation method and a particle beam irradiation apparatus in which depth direction irradiation field spread and lateral direction irradiation field spread are performed, an irradiation dose in each of irradiation layers of an irradiation target is made substantially constant, and control is simplified. 
     The depth direction irradiation field spread is made the active irradiation field spread in which plural irradiation layers having different ranges in an irradiation direction of the particle beam are superimposed, the lateral direction irradiation field spread is made the active irradiation field spread in which irradiation spots of the particle beam are superimposed in the lateral direction, and a bolus having a shape along a deepest part of the irradiation target in the depth direction is disposed to cross the particle beam.

TECHNICAL FIELD

The present invention relates to a particle beam irradiation methodapplied to the treatment of a cancer or the like, and a particle beamirradiation apparatus used for the same.

BACKGROUND ART

As the related art relating to this kind of particle beam irradiationmethod and particle beam irradiation apparatus, the following two papersare known. The first paper is the paper titled “Instrumentation fortreatment of cancer using proton and light-ion beams”, by W. T. Chu, etal., printed in the magazine “Review of Scientific Instruments”, 64(8),pp. 2055 to 2096, issued on August 1993.

The second paper is the paper titled “The 200-MeV proton therapy projectat the Paul Schrrer Institute: Conceptual design and practicalrealization”, by E. Pedoroni, et al., printed in the magazine “MedicalPhysics”, 22(1), pp. 37-53, issued on January 1995.

The first paper describes that in the case where various radiation beamsare transformed into thin diameter beams called pencil beams and areirradiated to a human body, the dose distributions of the radiationbeams in the body are changed as shown in FIG. 1. As shown in FIG. 1,among various radiations, a radiation beam with a small mass, such as anX-ray or a gamma ray, has a relative dose which becomes maximum in aportion close to the surface of the body, and is decreased as the depthfrom the surface of the body is increased. On the other hand, a particlebeam with a large mass, such as a proton beam or a carbon beam, has arelative dose which has a peak value at a position where the beam stopsat a deep portion from the surface of the body, that is, immediatelybefore the range of the particle beam. This peak value is called theBragg Peak (BP).

A particle beam cancer treatment method is such that this Bragg peak BPis irradiated to a tumor formed in a human organ and the treatment ofthe cancer is performed. In addition to the cancer, it can also be usedfor a case where a deep portion of a body is treated. A region to betreated, including a tumor, is generally called an irradiation target.The position of the Bragg peak is determined by the energy of anirradiated particle beam, and as the energy of the particle beam becomeshigh, the Bragg peak BP is formed at a deep position. In the particlebeam treatment, it is necessary that the particle beam is made to have auniform dose distribution over the whole of the irradiation target to beirradiated. In order to give the Bragg peak BP to the whole area of theirradiation target, “spread of irradiation field (radiation field)” ofthe particle beam is performed.

This “spread of irradiation field” is performed in three directions ofan X-axis, a Y-axis and a Z axis perpendicular to each other. When theirradiation direction of the particle beam is made the direction of theZ-axis, the “spread of irradiation field” is first performed in theZ-axis direction. The “spread of irradiation field” in the irradiationdirection of the radiation beam is generally called depth directionirradiation field spread. The second “spread of irradiation field” issuch that the irradiation field spread is performed in the X-axis andY-axis directions, and since the irradiation field spread is performedin the lateral direction perpendicular to the depth direction, it isgenerally called lateral direction irradiation field spread.

The depth direction irradiation field spread is performed to spread theBragg peak, which is in the irradiation direction of the particle beam,in the depth direction since the width of the Bragg peak BP in theirradiation direction of the particle beam is narrow as compared withthe extent of the irradiation target in the depth direction. On theother hand, the lateral direction irradiation field spread is performedto spread the Bragg peak BP in the direction perpendicular to theirradiation direction since the diameter of the particle beam is smallerthan the size of the irradiation target in the direction perpendicularto the irradiation direction. With respect to the depth directionirradiation field spread and the lateral direction irradiation fieldspread, methods described in the respective foregoing papers will bedescribed.

First, the lateral direction irradiation field spread includes a passivelateral direction irradiation field spread method and an active lateraldirection irradiation field spread method. The passive lateral directionirradiation field spread method is a method in which in a particle beamirradiation part of a particle beam irradiation apparatus, a particlebeam is irradiated to a scatterer to cause the particle beam to have anextent in the lateral direction, and a uniform dose portion of thecenter portion is cut out and is irradiated to the target region. In thecase where the uniform dose portion can not be made sufficiently largeby one scatterer, there is a case where the uniform dose portion isspread by two scatterers, and this is called a double scatterer method.Besides, there is also a method in which two deflection electromagnetsprovided at the upstream portion of a particle beam irradiation part ofa particle beam irradiation apparatus are used to scan the particle beamin a doughnut shape, and the particle beam scanned in the doughnut shapeis irradiated to the scatterer to spread the lateral directionirradiation field, and this is called a Wobbler System.

As the active lateral direction irradiation field spread method, thereis a method in which a deflection electromagnet provided at the upstreamportion of a particle beam irradiation part of a particle beamirradiation apparatus is used to scan the particle beam in the XY plane,and the irradiation position of the particle beam is moved with thelapse of time to obtain a wide irradiation field. In this method, auniform dose distribution can be obtained by suitably overlappingadjacent irradiation spots of thin diameter pencil beams. Scanningmethods of pencil beams include a raster method of performing scanningcontinuously with respect to time, and a spot method of performing astep-like scanning with respect to time. Incidentally, in this method,although the particle beam is generally called a pencil beam having athin diameter and is directly irradiated to the target region, there isalso a case where the diameter of the pencil beam is slightly enlargedby using a thin scatterer.

Next, the depth direction irradiation field spread will be described. Asdescribed before, the width of the Bragg peak BP in the irradiationdirection of the particle beam is narrow, and the width of the Braggpeak BP in the irradiation direction is spread by the depth directionirradiation field spread. The Bragg peak BP in which the width in theirradiation direction is spread is called spread-out Bragg peak. First,the depth direction passive irradiation field spread method includes amethod in which a comb-type energy modulator called a ridge filter or arange modulator is inserted so as to cross the particle beam.

In both the ridge filter and the range modulator, the thickness of thematerial of the energy modulator is modulated in the irradiationdirection of the particle beam. The ridge filter or the range moduledecreases the energy of the particle beam according to the modulatedthickness, and changes the energy according to the modulated thickness,and consequently, the particle beam in which various energies withdifferent intensities are mixed is irradiated to the irradiation target.Since the range of the particle beam is changed according to theintensity of the energy, the particle beam having various ranges can beirradiated to the irradiation target. In the passive depth directionirradiation field spread method as stated above, the spread-out Braggpeak SOBP in which the width is spread in the irradiation direction canbe obtained.

However, the width of the spread-out Bragg peak SOBP is constant in thelateral direction, that is, in the directions of the X and Y axesperpendicular to the irradiation direction of the particle beam, and itcan not be changed.

As another depth direction passive irradiation field spread method,there is a method in which a compensator called a bolus is used. Ingeneral, a region to be treated in a patient is positioned at themaximum depth of an affected organ in the depth direction, that is, atthe deepest part (boundary of the affected organ in the depth direction)of the affected organ in the Z-axis direction, and in general, the depthof the region to be treated has dependency in the lateral direction (X,Y-axis direction), and is changed in the X-axis and Y-axis directions.The change shape of the region to be treated in the depth direction iscalled a distal shape. As shown in FIG. 2, the bolus BL is an energymodulator which is fabricated for each patient in conformity with thisdistal shape, and is formed by using polyethylene or wax. By using thebolus BL, while the uniform irradiation dose is irradiated to the X, Yplane, the Bragg peak BP can be conformed to the distal shape.

FIG. 2( a) shows an irradiation target TV and a bolus BL. Theirradiation target TV has the deepest layer TVd, and the shape of thedeepest layer TVd is called the distal shape. Seven arrows indicatetypical particle beams. In FIG. 2( b), the doses of the seven typicalparticle beams to the irradiation target TV are indicated by a to g. Byusing the bolus BL, the dose distribution in the deepest layer TVd canbe flattened.

As the depth direction active irradiation field spread method, there isa method in which the energy of the particle beam itself irradiated froma particle beam irradiation apparatus is controlled, while the foregoingenergy modulator is not used. In this method, the energy of the particlebeam is controlled by changing the acceleration energy of an acceleratorto accelerate the particle beam, or the energy of the particle beam ischanged by inserting a tool called a range shifter so as to cross theparticle beam. There is also a method in which both the control of theaccelerator and the range filter are used.

In the depth direction active irradiation field spread method, theparticle beam is made the beam having the energy of specified intensity,and after the Bragg peak BP with a uniform dose is irradiated to oneirradiation layer of the irradiation target, the energy of the particlebeam is changed, and the Bragg peak BP is irradiated to an irradiationlayer next to the irradiation target TV. Such operation is repeatedplural times, and the Bragg peak BP of the particle beam is irradiatedto the plural irradiation layers, so that the spread-out Bragg peak SOBPhaving a desired width in the beam irradiation direction can beobtained. The depth direction active irradiation field spread method isa method in which in the state where the particle beam is not moved inthe X and Y-axis directions and is fixed to a definite irradiationposition, the energy of the particle beam is changed.

In order to obtain the spread-out Bragg peak SOBP having the desiredwidth, it is necessary to suitably adjust the dose of each irradiationlayer of the irradiation target TV, and the dose given to each layer iscalled “weighting of layer”. This “weighting of layer” is calculated bythe same method as the ridge filter or the range module. FIG. 3 shows anexample of the dose distribution in the depth direction and the“weighting of layer”. In FIG. 3, the vertical axis indicates therelative dose, and the horizontal axis indicates the depth in the body.A curved line indicated by a solid line indicates calculated values, andplural small squares indicate actually measured values. Plural straightlines extending in the vertical direction indicate the weightings in therespective irradiation layers. This example is a typical example, andthe “weighting of layer” is highest at the deepest part. When theweighting of the deepest part is 100, the weighting of the layeradjacent thereto is almost 10 or less.

A particle beam irradiation method in which the depth direction activeirradiation field spread method and the lateral direction activeirradiation field spread method are combined is described as a spotscanning technique on page 39 to page 45 of the second document.

According to the spot scanning technique, since the energy of theparticle beam can be controlled according to the movement of theparticle beam in the lateral direction (X, Y-axis direction), the widthof the spread-out Bragg peak SOBP in the irradiation direction can alsobe changed in the lateral direction. Besides, since the energy of theparticle beam can also be changed so that the range of the particle beamconforms to the distal shape of a region to be treated, a bolus is notused in the spot scanning technique.

Non-patent document 1: paper titled “Instrumentation for treatment ofcancer using proton and light-ion beams”, by W. T. Chu, et al., printedin the magazine “Review of Scientific Instruments”, 64(8), pp. 2055 to2096, issued on August 1993.

Non-patent document 2: paper titled “The 200-MeV proton therapy projectat the Paul Schrrer Institute: Conceptual design and practicalrealization”, by E. Pedoroni, et al., printed in the magazine “MedicalPhysics”, 22(1), pp. 37-53, issued on January 1995.

Disclosure of the Invention

Problems that the Invention is to Solve

However, in the spot scanning technique, since the energy of theparticle beam is controlled while the particle beam is moved in thelateral direction (X, Y-axis direction), a portion with a high weightingand a portion with a low weighting are mixed in the same irradiationlayer, and accordingly, accurate control of an irradiation dose isdifficult, and it is difficult to accurately irradiate an irradiationtarget with a desired relative dose.

Means for Solving the Problems

A particle beam irradiation method of the invention is a particle beamirradiation method which uses both a depth direction irradiation fieldspread for spreading an irradiation field of a particle beam in a depthdirection along an irradiation direction of the particle beam, and alateral direction irradiation field spread for spreading the irradiationfield of the particle beam in a lateral direction perpendicular to theirradiation direction of the particle beam, and irradiates the particlebeam to an irradiation target. In the particle beam irradiation method,the depth direction irradiation field spread is an active irradiationfield spread in which plural irradiation layers having different rangesin the irradiation direction of the particle beam are superimposed, thelateral direction irradiation field spread is an active irradiationspread in which irradiation spots of the particle beam are superimposedin the lateral direction, and a bolus having a shape along a deepestpart of the irradiation target in the depth direction is disposed tocross the particle beam.

Besides, a particle beam irradiation apparatus of the invention is aparticle beam irradiation apparatus including a particle beam generationpart for generating a particle beam, a particle beam transport part fortransporting the particle beam generated by the particle beam generationpart, a particle beam irradiation part for irradiating the particle beamtransported by the particle beam transport part to an irradiationtarget, depth direction irradiation field spread means for spreading anirradiation field of the particle beam in a depth direction along anirradiation direction of an irradiation direction of the particle beam,and lateral direction irradiation field spread means for spreading theirradiation field of the particle beam in a lateral directionperpendicular to the irradiation direction of the particle beam. In theparticle beam irradiation apparatus, the depth direction irradiationfield spread means is active depth direction irradiation field spreadmeans for superimposing plural irradiation layers having differentranges in the irradiation direction of the particle beam, the lateraldirection irradiation field spread means is active irradiation fieldspread means for superimposing irradiation spots of the particle beam inthe lateral direction, and a bolus having a shape along a deepest partof the irradiation target in the depth direction is disposed to crossthe particle beam.

Effects of the Invention

In the particle beam irradiation method of the invention, the depthdirection irradiation field spread is the active irradiation fieldspread in which the plural irradiation layers with the different rangesin the irradiation direction of the particle beam are superimposed, thelateral direction irradiation field spread is the active irradiationfield spread in which the irradiation spots of the particle beam aresuperimposed in the lateral direction, and the bolus having the shapealong the deepest part of the irradiation target in the depth directionis disposed to cross the particle beam, and therefore, the irradiationdose to be given to the deepest layer of the irradiation target and eachof the irradiation layers adjacent thereto can be kept substantiallyconstant in each of the irradiation layers, and the control can besimplified.

Besides, in the particle beam irradiation apparatus of the invention,the depth direction irradiation field spread means is the active depthdirection irradiation field spread means for superimposing the pluralirradiation layers with the different ranges in the irradiationdirection of the particle beam, the lateral direction irradiation fieldspread means is the active irradiation field spread means forsuperimposing the irradiation spots of the particle beam in the lateraldirection, and the bolus having the shape along the deepest part of theirradiation target in the depth direction is disposed to cross theparticle beam, and therefore, the irradiation dose to be given to thedeepest layer of the irradiation target and each of the irradiationlayers adjacent thereto can be kept substantially constant in each ofthe irradiation layers, and the control can be simplified.

Best Mode For Carrying Out The Invention

Hereinafter, some embodiments of the invention will be described withreference to the drawings.

EMBODIMENT 1

First, embodiment 1 of the invention will be described. In thisembodiment 1, the embodiment 1 of a particle beam irradiation apparatusof the invention will be described, and further, the embodiment 1 of aparticle beam irradiation method of the invention will be described.

This embodiment 1 is characterized in that an active depth directionirradiation field spread and an active lateral direction irradiationfield spread are combined, and in addition to these, a bolus having ashape of a deepest part of an irradiation target in a depth direction isused.

FIG. 4 shows the whole structure of the embodiment 1 of the particlebeam irradiation apparatus used for carrying out the embodiment 1 of theparticle beam irradiation method of the invention. As shown in FIG. 4,the embodiment 1 of the particle beam irradiation apparatus includes aparticle beam generation part 10, a particle beam transport part 20, andthree particle beam irradiation parts 30A, 30B and 30C. For reasons ofapplication of radiation safety management and the like, the particlebeam generation part 10 and the particle beam irradiation parts 30A, 30Band 30C are installed in individual shielded rooms. The particle beamtransport part 20 connects the particle beam generation part 10 to therespective particle beam irradiation parts 30A, 30B and 30C. Theacceleration particle beam transport part 20 includes particle beamtransport passages 21, 22 and 23 to transport the particle beamgenerated in the particle beam generation part 10 to the respectiveparticle beam irradiation parts 30A, 30B and 30C. The particle beamtransport passages 21, 22 and 23 are constructed of vacuum ducts. Theparticle beam irradiation parts 30A, 30B and 30C irradiate the particlebeam PB to a target region TV of a patient.

The particle beam generation part 10 includes an ion source 11 and anaccelerator 12. The ion source 11 generates the particle beam with largemass, such as a proton beam or a carbon beam. The accelerator 12accelerates the particle beam generated in the ion source 11, and formsthe particle beam PB. An energy setting controller 13 is electricallyconnected to the accelerator 12. The energy setting controller 13supplies an energy control signal ES to the accelerator 12, sets andcontrols the acceleration energy of the particle beam PB given by theaccelerator 12, and constitutes active depth direction irradiation fieldspread means 15. The active depth direction irradiation field spreadmeans 15 is controlled by a control calculator to control the wholeapparatus, and performs a control to superimpose plural irradiationlayers having different ranges in the depth direction. The irradiationenergy of the particle beam is changed for each of the pluralirradiation layers, and the spread-out Bragg peak SOBP is formed in theirradiation direction of the particle beam PB, that is, in the Z-axisdirection.

The particle beam irradiation parts 30A, 30B and 30C constitute atreatment room 1, a treatment room 2, and a treatment room 3,respectively. The three particle beam irradiation parts 30A, 30B and 30Chave the same structure one another, and each of them includes anirradiation nozzle 31, a treatment stand 32, and a positioning device33. The treatment stand 32 is used for keeping a patient in the state ofa dorsal position or a sitting position, and the positioning device 33is used for confirming the position of an affected organ by an X-rayapparatus or the like. The irradiation nozzle 31 irradiates the particlebeam PB transported to the particle beam irradiation parts 30A, 30B, 30Cto the irradiation target TV of the patient on the treatment stand 32.

FIG. 5 shows the specific structure of the irradiation nozzle 31 of eachof the particle beam irradiation parts 30A, 30B and 30C in theembodiment 1. The irradiation nozzle shown in FIG. 5 is denoted bysymbol 31A. The irradiation nozzle 31A shown in FIG. 5 includesdeflection electromagnets 41 a and 41 b to scan the particle beam PB ina lateral direction, that is, on the X, Y plane perpendicular to theirradiation direction of the particle beam PB, beam position monitors 42a and 42 b to monitor the irradiation position of the particle beam PB,a dose monitor 43 to monitor the irradiation dose of the particle beamPB, and a bolus attachment stand 44. A bolus 45 is attached to the bolusattachment stand 44.

An arrow PB of FIG. 5 indicates the irradiation direction of theparticle beam PB. The deflection electromagnets 41 a and 41 b aredisposed to be adjacent to each other at the upstream side in theirradiation direction. The beam position monitors 42 a and 42 b aredisposed to be spaced from each other in the irradiation direction, andthe dose monitor 43 is disposed between the beam position monitors 42 aand 42 b and near the beam position monitor 42 b. The bolus attachmentstand 44 is disposed nearest a patient and at the downstream side in theirradiation direction.

The deflection electromagnets 41 a and 41 b shown in FIG. 5 constitutelateral direction active irradiation field spread means 40 for spreadingthe Bragg peak BP of the particle beam PB in the lateral directionperpendicular to the irradiation direction. The lateral direction activeirradiation field spread means 40 forms the spread-out SOBP in thelateral direction perpendicular to the irradiation direction of theparticle beam BP, that is, in the X-axis and Y-axis directions.Specifically, the particle beam PB is scanned in the lateral direction,that is, on the XY plane, the irradiation spots are superimposed in thelateral direction, and the spread-out SOBP is formed on the XY plane.

The bolus 45 attached to the bolus attachment stand 44 has a shape alongthe distal shape of the deepest part of the irradiation target TV, thatis, a region to be treated. The bolus 45 is an energy modulatorfabricated for each patient and is formed by using polyethylene or wax.The bolus 45 is disposed so as to cross the particle beam PB irradiatedfrom the irradiation nozzle 31A to the irradiation target TV of thepatient, and by using the bolus 45, the irradiation dose to the deepestlayer TVd of the irradiation target TV and each of the irradiationlayers adjacent thereto can be flattened.

The feature of the embodiment 1 is that the active depth directionirradiation field spread means 15 and the active lateral directionirradiation field spread means 40 are combined with the bolus 45. Thecombination of the active depth direction irradiation field spread andthe active lateral direction irradiation field spread is known as thespot scanning technique. In this embodiment 1, the bolus 45 is furthercombined therewith and is used. Also as shown in FIG. 3, layer weightingto plural irradiation layers is highest for the deepest layer TVd, andin the case where the weighting of the deepest layer TVd is made 100,the weighting of each of irradiation layers adjacent thereto is ⅕ orless. In this embodiment 1, the irradiation dose to the deepest layerTVd of the irradiation target TV and each of the irradiation layersadjacent thereto can be flattened by using the bolus 45. Thus, theirradiation dose to the deepest layer TVd and each of the irradiationlayers adjacent thereto is kept constant in each of the irradiationlayers, and irradiation can be performed. Thus, in the active depthdirection irradiation field spread means 15, although the irradiationdose of each of the irradiation layers is changed according to eachirradiation layer, the irradiation energy can be kept substantiallyconstant in each of the irradiation layers, and the control can besimplified.

The particle beam irradiation method of the embodiment 1 will bedescribed in contrast to the conventional spot scanning technique. FIGS.6( a) and 6(b) show the irradiation method of the embodiment 1, andFIGS. 7( a) and 7(b) show the conventional spot scanning technique. FIG.6( a) and FIG. 7( a) show the shapes of irradiation targets, and asemicircular irradiation target TV is supposed in each of them. Adeepest layer TVd is a surface portion of this semicircular irradiationtarget TV. FIG. 8 shows the shape of the bolus 45 used for irradiationto the irradiation target TV shown in FIGS. 6( a) and 6(b).

FIG. 6( b) schematically shows the irradiation method of the particlebeam PB according to the embodiment 1, and FIG. 7( b) schematicallyshows the irradiation method of the particle beam PB according to theconventional spot scanning technique. In FIG. 6( b) and FIG. 7( b),plural small circles S indicate irradiation spots each corresponding tothe diameter of the particle beam PB. Although these irradiation spotsare actually scanned such that the irradiation spots adjacent to eachother partially overlap with each other, for simplification of thedrawings, they are shown in a state where there is no overlap. Besides,although the number of the irradiation spots S is actually larger, theyare shown while the number is made smaller than an actual one.

In FIG. 6( b) and FIG. 7( b), the X-axis in the lateral directionrelative to the particle beam PB is indicated by a line X-X, and theY-axis is indicated by a line Y-Y. Addresses of from 1 to 12 areassigned along the line X-X, and addresses of from A to P are assignedalong the line Y-Y. The deepest layer TVd of the irradiation target TVshown in FIG. 6( a) is indicated by a large circle TVd, and pluralirradiation spots S in the inside of the circle TVd or partiallyoverlapping with this circle TVd are indicated by small circles S ofsolid lines. These small circles S of the solid lines are the particlebeams PB corresponding to the deepest layer TVd of the irradiationtarget TV, and these are irradiated with substantially the same energydose in one scanning on the X, Y plane.

In FIG. 6( b), the irradiation spots S are basically scanned fromaddress A1 along the line X-X, a shift is made from address A12 toaddress B1, and the scanning is performed to the final address P12. Withrespect to the deepest layer TVd, only the irradiation spots S indicatedby the small circles of the solid lines are scanned with the sameirradiation dose. The irradiation to the deepest layer TVd is achievedby scanning the irradiation spots S corresponding to the circle TVdwhile the same irradiation dose is held.

In the conventional spot scanning technique, since the bolus 45 is notused, with respect to the irradiation depth D (see FIG. 7( a)) of thesame semicircular irradiation target TV, plural annular portions TV1 toTV 4 different in depth are supposed as shown in FIGS. 7( a) and 7(b).In the case where the irradiation spots S are scanned with respective tothe annular portions TV1 to TV4, since, for example, addresses B6 and B7correspond to the deepest layer TVd, it is necessary to make theirradiation dose high. However, since, for example, addresses C6 and C7are shallower than the deepest layer TVd, the irradiation dose to begiven is made small. In the line of address F, since addresses F2 andF11 correspond to the deepest layer TVd, the high irradiation dose isgiven. However, since addresses F3 and F10 correspond to the shallowlayer adjacent to the deepest layer TVd, it is necessary to make theirradiation dose small. Besides, since addresses F4 and F9 are furthershallow layers adjacent to the addresses F3 and F10 when viewed from thedeepest layer TVd, it is necessary to further make the irradiation dosesmall.

As stated above, in the conventional spot scanning technique, when thearea of the same irradiation depth D is scanned, it is necessary tofrequently change the irradiation dose. With respect to the irradiationdose, the beam current is changed in the accelerator 12 by the depthdirection irradiation field spread means 15, however, it is difficult toperform the frequent change of the beam current without error.

As an active lateral direction irradiation field spread method, in thecase where a spot method is adopted in which the particle beam PB isscanned stepwise, the irradiation dose given to each irradiation spot Sis controlled by the irradiation time. The control device of theirradiation dose has values of planned dose corresponding to therespective irradiation spots S in a tabular form, and the particle beamof each irradiation spot S is temporarily stopped at the time point whenthe irradiation dose reaches the planned dose. Although the irradiationdose can be controlled by the irradiation time as stated above, in orderto accurately control the irradiation dose, the accelerator 12 suppliesthe beam current suitable for the planned dose of the irradiation spot Sand further, the beam current must be accurately controlled.

In the control of the beam current of the accelerator 12 as statedabove, in the conventional spot scanning technique, the beam current ismade large in the portions corresponding to the deepest layer TVd, suchas the addresses F2 and F11 of FIG. 7( b), and the beam current issequentially made small in the addresses F3 and F10 and the addresses F4and F9. However, since the adjustment of the beam current of theaccelerator 12 can not be instantaneously performed, in order to changethe beam current with respect to a certain depth D, it is necessary toprolong the irradiation time, and there is a problem that the controlbecomes complicated.

On the other hand, like the embodiment 1, when the active depthdirection irradiation field spread means 15 and the active lateraldirection irradiation field spread means 40 are combined with the bolus45, the irradiation dose to be given to the irradiation spot S can bekept substantially constant in the deepest layer TVd and each of theirradiation layers adjacent thereto, and the beam current of theaccelerator 12 can be kept substantially constant with respect to eachof the irradiation layers. Accordingly, the control can be simplified.

Incidentally, the dose distribution and the specific numerical values ofthe weighting described here are an example, and the effect of theembodiment 1 of the invention does not depend on the specific numericalvalues.

EMBODIMENT 2

Next, embodiment 2 of the invention will be described. Also in theembodiment 2, the embodiment 2 of a particle beam irradiation apparatusof the invention will be described, and further, the embodiment 2 of aparticle beam irradiation method of the invention will be described.

The embodiment 2 of the particle beam irradiation apparatus used for theembodiment 2 of the particle beam irradiation method of the invention isalso characterized in that an active depth direction irradiation fieldspread and an active lateral direction irradiation field spread arecombined, and further, a bolus 45 is combined and is used, andreirradiation is performed once or more to a deepest layer TVd of anirradiation target.

In the particle beam irradiation apparatus of the embodiment 2, inaddition to the active depth direction irradiation field spread means 15in the particle beam irradiation apparatus of the embodiment 1, activedepth direction irradiation field spread means 60 is added. The particlebeam irradiation apparatus of the embodiment 2 is constructed similarlyto the embodiment 1 except the above.

In the particle beam irradiation apparatus of the embodiment 2, theactive depth direction irradiation field spread means 15 and 60superimpose plural irradiation layers having different ranges in theirradiation direction of the particle beam PB, that is, in the depthdirection, and form the spread-out Bragg peak SOBP in the depthdirection. Similarly to the embodiment 1, the bolus 45 makes theirradiation dose to the deepest layer TVd and each of the irradiationlayers adjacent thereto substantially constant, and simplifies thecontrol of the depth direction irradiation field spread means 15 and 60.

FIG. 9 shows the structure of an irradiation nozzle 31 used in theparticle beam irradiation apparatus of the embodiment 2 of theinvention. The irradiation nozzle of FIG. 9 is denoted by symbol 31B. Asis apparent from FIG. 9, the irradiation nozzle 31B used in theembodiment 2 includes deflection electromagnets 51 a and 51 b to scan aparticle beam PB on the X, Y plane, beam position monitors 52 a and 52 bto monitor the irradiation position of the particle beam PB, a dosemonitor 53 to monitor the irradiation dose of the particle beam PB, abolus attachment stand 54, a range shifter 56, and a variable collimator57.

Similarly to the deflection electromagnets 41 a and 41 b shown in FIG.5, the deflection electromagnets 51 a and 51 b shown in FIG. 9constitute the lateral direction active irradiation field spread means50 for spreading the Bragg peak BP of the particle beam PB in thelateral direction perpendicular to the irradiation direction. Similarlyto the active lateral direction irradiation field spread means 40 of theembodiment 1, the lateral direction active irradiation field spread mean50 forms the spread-out SOBP in the lateral direction perpendicular tothe irradiation direction of the particle beam PB, that is, in theX-axis, Y-axis direction. Specifically, the particle beam PB is scannedin the lateral direction, that is, on the XY plane, the irradiationspots are superimposed in the lateral direction, and the spread-out SOBPis formed on the XY plane.

The range shifter 56 constitutes the active depth direction irradiationfield spread means 60. The range shifter 56 is inserted so as to crossthe particle beam PB, decreases the energy of the particle beam PBaccording to an adjustment signal supplied thereto, and spreads theirradiation field in the depth direction. In the embodiment 2, theactive depth direction irradiation field spread means 15 is formed ofthe energy setting controller 13 to the accelerator 12, and the activedepth direction irradiation field spread means 60 is formed of the rangeshifter 56. By using both of them, the sufficient irradiation fieldspread in the depth direction can be obtained. However, one of these cannon be used.

The variable collimator 57 is for limiting the irradiation field in thelateral direction, is moved in an arrow A direction by remote control,and adjusts the irradiation field in the lateral direction. As thevariable collimator 57, for example, a multilobed collimator is used.The irradiation field in the lateral direction is adjusted by thevariable collimator 57, so that a three-dimensional dose distribution isformed.

An arrow PB of FIG. 9 indicates the irradiation direction of theparticle beam PB. The deflection electromagnets 51 a and 51 b aredisposed to be adjacent to each other at the upstream side. The beamposition monitors 52 a and 52 b are disposed to be spaced from eachother, and the dose monitor 53 is disposed between the beam positionmonitors 52 a and 52 b and near the beam position monitor 52 b. Thebolus attachment stand 54 is disposed nearest the patient and at thedownstream side, and a bolus 45 is attached to the bolus attachmentstand 54. The range shifter 56 is disposed between the dose monitor 53and the beam position monitor 52 a and near the dose monitor 53. Thevariable collimator 57 is disposed between the beam position monitor 52b and the bolus attachment stand 54.

In this embodiment 2, the active depth direction irradiation fieldspread means 15 and 60 and the active lateral direction irradiationfield spread means 50 are combined, and further, the bolus 45 iscombined with these. Similarly to the embodiment 1, the bolus 45 makesthe irradiation dose to the deepest layer TVd and each of theirradiation layers adjacent thereto substantially constant, andsimplifies the control of the depth direction irradiation field spreadmeans 15 and 60.

In the embodiment 2, it is important that the superposition of theirradiation doses to the deepest layer TVd of the irradiation target TVin the depth direction is controlled as planned. However, since anaffected organ moves based on the physiological activity, such as breathof the patient or blood flow in the body, and the irradiation target TVis also displaced according to this, there is a possibility that anerror occurs in the superposition of the irradiation doses. For example,although the position of the liver is periodically displaced mainly inthe length direction of the body by the breath, it is also periodicallydisplaced in the thickness direction of the body.

In the particle beam irradiation method according to the embodiment 2,reirradiation is performed once or more to the deepest layer TVd. Sincethe irradiation dose given to the deepest layer TVd is 5 to 20 times aslarge as that of the other irradiation layer, when the irradiation doseto the deepest layer TVd is made accurate, the accuracy of the wholeirradiation dose distribution can be improved.

In the embodiment 2, the particle beam PB is irradiated in theirradiation procedure shown in FIG. 10. This control procedure is storedin a storage device of a control calculator to control the wholeapparatus. In FIG. 10, respective irradiation layers of from the deepestlayer TVd to the second layer, the third layer, . . . , the ninth layerare arranged along the vertical column, sequence of irradiations of thefirst, the second, . . . , the fifth is arranged in the horizontalcolumn, and irradiation sequences are written as 1, 2, 3, . . . , 13 atthe intersection points of the respective irradiation layers and therespective sequence of irradiations. The irradiation of the particlebeam PB is executed in order of the irradiation sequences 1, 2, 3, . . ., 13.

In the irradiation procedure of FIG. 10, the first irradiation includesthe irradiation of the irradiation sequence 1 to the deepest layer TVdand the irradiations of the irradiation sequences 2, 3, 4, 5, 6, 7, 8and 9 to the respective layers of from the second layer to the ninthlayer. The second irradiation includes the irradiation of theirradiation sequence 10 to the deepest layer TVd, the third irradiationincludes the irradiation of the irradiation sequence 11 to the deepestlayer TVd, and the fourth and fifth irradiations respectively includethe irradiations of the irradiation sequences 12 and 13 to the deepestlayer TVd. All the irradiations of the irradiation sequences 10, 11, 12and 13 are reirradiations to the deepest layer TVd.

Each of the five irradiations of the irradiation sequences 1, 10, 11, 12and 13 to the deepest layer TVd is performed with a dose of ⅕ of ahighest irradiation dose RV1 corresponding to the deepest layer TVd, andthe total irradiation dose becomes RV1. Irradiation doses RV2 to RV9 tothe layers of from the second layer to the ninth layer are sequentiallydecreased from the irradiation dose RV1. In FIG. 10, the number of timesof irradiation to the deepest layer TVd is made five, the necessaryirradiation dose RV1 is divided into five equal parts, and the fiveirradiations are performed with an irradiation dose of RV/5.

FIGS. 11( a), 11(b), 11(c) and 11(d) are diagrams showing theimprovement situation of the error of an irradiation dose due to thedisplacement of the irradiation target TV in the case where the numberof times of irradiation to the deepest layer TVd is two in total, thatis, the number of times of reirradiation is 1.

In FIG. 11( a), the irradiation target TV is indicated, and it isassumed that the irradiation target TV is displaced with the breath inthe direction of an arrow B along an axis 206. In FIG. 11( b), the firstdistribution of an irradiation dose is indicated by a solid line curve201, and the second distribution of an irradiation dose is indicated bya dotted line curve 202. FIG. 11( c) shows the first distribution 201 ofthe irradiation dose, and a curve 203 of the distribution of the totalirradiation dose in which the first and the second irradiation doses areadded.

In FIG. 11( d), the distribution of an irradiation dose in a case wherethe irradiation to the deepest layer TVd is executed only once isindicated by a curve 205, and the curve 205 and the curve 203 arecompared with each other. A gray flow area 204 shown in FIG. 11( d)indicates an area where in the curve 205, an irradiation dose largerthan the curve 203 is given by the displacement of the irradiationtarget TV.

As stated above, in the case where the irradiation is performed onlyonce to a certain irradiation layer such as the deepest layer TVd, thereis a danger that an excessive irradiation dose is given in the area 204by the displacement of the irradiation target TV. However, by thereirradiation, division is made into plural parts, and when theirradiation is performed with the equally divided irradiation dose, theoccurrence of the excessive irradiation area 204 as stated above can beprevented.

In the example of FIG. 11, for simplifying the explanation, there isused a distribution in which the dose is decreased linearly from 100% to0% at both ends of the curves 201, 202, 203 and 205 of the dosedistribution. Actually, although the end of the dose distribution isclose to the convoluted function of the Gaussian distribution, thisexplanation does not depend on a specific mathematical expression. Whenthe number of times of irradiation to the deepest layer TVd is furtherincreased, the dose distribution is further improved. Also with respectto the depth direction, similarly, when the irradiation is performedplural times, the irradiation distribution can be improved.

In this embodiment 2, the active depth direction irradiation fieldspread and the active lateral direction irradiation field spread arecombined and the particle beam PB is irradiated, and in this case,respective irradiation spots S are individually irradiated and aresuperimposed in both the depth direction and the horizontal direction.

Besides, in this embodiment 2, since the superposition of theirradiation spots is required not only in the depth direction but alsoin the lateral direction, there is a tendency that a time required forirradiation becomes long. In order to shorten the time required for theirradiation and to reduce irradiation error due to the physiologicalactivity of the patient, in the embodiment 2, plural irradiations areperformed only to the deepest layer TVd.

In the conventional spot scanning technique in which the active depthdirection irradiation field spread and the active lateral directionirradiation field spread are combined, since the bolus 45 is not used,as shown in FIGS. 7( a) and 7(b), the deepest layer TVd exists only atthe outer peripheral part of each of the irradiation layers in which theirradiation depth D (see FIG. 7( a)) is changed. Thus, in theconventional spot scanning technique, in order to re-irradiate thedeepest layer TVd, the reirradiation is required to be performed withrespect to many irradiation layers, and the energy of the accelerator 12is required to be adjusted with respect to the respective irradiationlayers in which the irradiation depth D is changed, and the complicatedcontrol is required.

In the embodiment 2, since the bolus 45 is used, as shown in FIG. 6( b),the deepest layer TVd can be concentrated into one layer, and theadjustment of energy of the accelerator 12 and the adjustment of therange shifter 56 are unnecessary in the irradiation of the deepest layerTVd, and therefore, the whole deepest layer TVd can be easilyre-irradiated.

As stated above, according to the embodiment 2, also with respect to theirradiation target TV which is displaced based on the physiologicalactivity such as the breadth of the patient, while the irradiationaccuracy of the irradiation spot S is held, it is possible to preventthe irradiation time from being prolonged.

As stated above, in the embodiment 2, the deepest layer TVd isre-irradiated once or more, and the number of times of irradiation ismade plural, so that the error of the irradiation dose due to thedisplacement of the target region TV can be reduced.

Incidentally, the dose distribution and the specific numerical values ofthe weighting described here are an example, and the effect of theinvention does not depend on the specific numerical values.

EMBODIMENT 3

Next, embodiment 3 of the invention will be described. Since a particlebeam irradiation apparatus used for the embodiment 3 is the same as thatexplained in the embodiment 1 or the embodiment 2, the embodiment 3 of aparticle beam irradiation method of the invention will be mainlydescribed in the embodiment 3.

In the embodiment 3, a particle beam PB is irradiated in an irradiationprocedure shown in FIG. 12. The control procedure is also stored in thestorage device of the control calculator to control the whole apparatus.In FIG. 12, respective irradiation layers of from the deepest layer TVdto the second layer, the third layer, . . . , the ninth layer arearranged along the vertical column, the sequence of irradiations of thefirst, the second, . . . , the fifth is arranged in the horizontalcolumn, and irradiation sequences are written as 1, 2, 3, . . . , 16 atintersection points of the respective irradiation layers and therespective sequence of irradiations. The irradiation of the particlebeam PB is executed in order of the irradiation sequences 1, 2, 3, . . ., 16.

In the irradiation procedure of FIG. 12, the first irradiation includesthe irradiation of the irradiation sequence 1 to the deepest layer TVd,and the irradiations of the irradiation sequences 2, 3, 4, 5, 6, 7, 8and 9 to the second layer to the ninth layer. The second irradiationincludes the irradiation of the irradiation sequence 10 to the deepestlayer TVd, and the irradiations of the irradiation sequences 11 and 12to the second layer and the third layer. The third irradiation includesthe irradiation of the irradiation sequence 13 to the deepest layer TVd,and the irradiation of the irradiation sequence 14 to the second layer.The fourth irradiation includes the irradiation of the irradiationsequence 15 to the deepest layer TVd, and the fifth irradiation includesthe irradiation of the irradiation sequence 16 to the deepest layer TVd.

All the four irradiations of the irradiation sequences 10, 13, 15 and 16are reirradiations to the deepest layer TVd, the two irradiations of theirradiation sequences 11 and 14 are reirradiations to the second layer,and the irradiation of the irradiation sequence 12 is the reirradiationto the third layer.

Each of, in total, five irradiations of the irradiation sequences 1, 10,13, 15 and 16 to the deepest layer TVd is performed with a dose of ⅕ ofa highest irradiation dose RV1 corresponding to the deepest layer TVd,and the total irradiation dose becomes RV1. Each of, in total, threeirradiations of the irradiation sequences 2, 11 and 14 to the secondlayer is performed with a dose of ⅓ of a irradiation dose RV2 necessaryfor the second layer, and the total irradiation dose becomes RV2. Eachof the irradiations of the irradiation sequences 3 and 12 to the thirdlayer is performed with a dose of ½ of an irradiation dose RV3 necessaryfor third layer, and the total irradiation dose becomes RV3. Theirradiation doses RV2 to RV9 for the second layer to the ninth layer aresequentially decreased from the irradiation dose RV1 for the deepestlayer TVd, and the irradiation doses RV2 and RV3 for the second layerand the third layer are high as compared with the irradiation doses forthe fourth layer to the ninth layer.

As stated above, in the embodiment 3, the reirradiation is performedonce or more to the deepest layer TVd, and to the second layer and thethird layer having the high irradiation doses subsequently thereto. Evenin the case where the irradiation target TV is displaced by thephysiological activity such as breath, the irradiation error to thedeepest layer TVd, the second layer and the third layer can be reduced.

EMBODIMENT 4

Next, embodiment 4 of the invention will be described. Since a particlebeam irradiation apparatus used in this embodiment 4 is the same as thatdescribed in the embodiment 1 or the embodiment 2, the embodiment 4 of aparticle beam irradiation method of the invention will be mainlydescribed also in the embodiment 4.

In this embodiment 4, a particle beam PB is irradiated in an irradiationprocedure shown in FIG. 13. This control procedure is also stored in thestorage device of the control calculator to control the whole apparatus.In FIG. 13, respective irradiation layers of from the deepest layer TVdto the second layer, the third layer, . . . , the ninth layer arearranged along the vertical column, the sequence of irradiations of thefirst, the second, . . . , the fifth is arranged in the horizontalcolumn, and irradiation sequences are written as 1, 2, 3, . . . , 16 atintersection points between the respective irradiation layers and therespective sequence of irradiations. The irradiation of the particlebeam PB is executed in order of the irradiation sequences 1, 2, 3, . . ., 16.

In the irradiation procedure of FIG. 13, the first irradiation includesthe irradiation of the irradiation sequence 1 to the deepest layer TVdand the irradiations of the irradiation sequences 2, 3, 4, 5, 6, 7, 8and 9 to the second layer to the ninth layer. The second irradiationincludes the irradiation of the irradiation sequence 10 to the deepestlayer TVd and the irradiations of the irradiation sequences 14 and 16 tothe second layer and the third layer. The third irradiation includes theirradiation of the irradiation sequence 11 to the deepest layer TVd andthe irradiation of the irradiation sequence 15 to the second layer. Thefourth irradiation includes the irradiation of the irradiation sequence12 to the deepest layer TVd, and the fifth irradiation includes theirradiation of the irradiation sequence 13 to the deepest layer Tvd.

All the irradiations of the irradiation sequences 10, 11, 12 and 13 arereirradiations to the deepest layer TVd, the irradiations of theirradiation sequences 14 and 15 are reirradiations to the second layer,and the irradiation of the irradiation sequence 16 is reirradiation tothe third layer.

Each of, in total, five irradiations of the irradiation sequences 1, 10,11, 12 and 13 to the deepest layer TVd is performed with a dose of ⅕ ofa highest irradiation dose RV1 corresponding to the deepest layer TVd,and the total irradiation dose becomes RV1. Each of, in total, threeirradiations of the irradiation sequences 2, 14 and 15 to the secondlayer is performed with a dose of ⅓ of an irradiation dose RV2 necessaryfor the second layer, and the total irradiation dose becomes RV2. Eachof the irradiations of the irradiation sequences 3 and 16 to the thirdlayer is performed with a dose of ½ of an irradiation dose RV3 necessaryfor the third layer, and the total irradiation dose becomes RV3. Theirradiation doses RV2 to RV9 for the second layer to the ninth layer aresequentially decreased from the irradiation dose RV1 for the deepestlayer TVd, and the irradiation doses RV2 and RV3 for the second layerand the third layer are high as compared with the irradiation doses forthe fourth layer to the ninth layer.

In this embodiment 4, after the four reirradiations of the irradiationsequences 10 to 13 to the deepest layer TVd are completed, the tworeirradiations of the irradiation sequences 14 and 15 to the secondlayer are performed. Further, thereafter, the irradiation of theirradiation sequence 16 to the third layer is performed. Also in thisembodiment 4, since the reirradiation is performed once or more to thedeepest layer TVd and to the second layer and the third layer havinghigh irradiation doses subsequently thereto, even if the irradiationtarget TV is displaced by the physiological activity such as breadth,the irradiation error to the deepest layer TVd, the second layer and thethird layer having the high irradiation doses can be reduced.

EMBODIMENT 5

Next, embodiment 5 of the invention will be described. Since a particlebeam irradiation apparatus used in this embodiment is the same as thatexplained in the embodiment 1 or the embodiment 2, the embodiment 5 of aparticle beam irradiation method of the invention will be mainlydescribed also in the embodiment 5.

In this embodiment 5, a particle beam PB is irradiated in an irradiationprocedure shown in FIG. 14. This control procedure is also stored in thestorage device of the control calculator to control the whole apparatus.In FIG. 14, respective irradiation layers of from the deepest layer TVdto the second layer, the third layer, . . . , the ninth layer arearranged along the vertical column, and weightings (relative values) tothe respective irradiation layers, and next thereto, the sequence ofirradiations of the first, the second, the tenth are arranged in thehorizontal columns thereof. Irradiation sequences are written as 1, 2,3, . . . , 24 at intersection points of the respective irradiationlayers and the respective sequence of irradiations. The irradiation ofthe particle beam PB is performed in order of the irradiation sequences1, 2, 3, . . . , 24.

In the irradiation procedure of FIG. 14, the first irradiation includesthe irradiation of the irradiation sequence 1 to the deepest layer TVdand the irradiations of the irradiation sequences 2, 3, 4, 5, 6, 7, 8and 9 to the respective layers of from the second layer to the ninthlayer. The second irradiation includes the irradiation of theirradiation sequence 10 to the deepest layer TVd and the irradiations ofthe irradiation sequences 11, 12, 13 and 14 to the respective layers offrom the second layer to the fifth layer. The third irradiation includesthe irradiation of the irradiation sequence 15 to the deepest layer TVdand the irradiations of the irradiation sequences 16 and 17 to thesecond layer and the third layer. The forth to the tenth irradiationsare respectively irradiations of the irradiation sequences 18, 19, 20,21, 22, 23 and 24 to the deepest layer TVd.

All the nine irradiations of the irradiation sequences 10, 15 and 18 to24 are reirradiations to the deepest layer TVd, the two irradiations ofthe irradiation sequences 11 and 16 are reirradiations to the secondlayer, and the two irradiations of the irradiation sequences 12 and 17are reirradiations to the third layer. The irradiations of theirradiation sequences 13 and 14 are respectively reirradiations to thefourth layer and the fifth layer.

Each of, in total, ten irradiations of the irradiation sequences 1, 10,15 and 18 to 24 to the deepest layer TVd is performed with a dose of1/10 of a highest irradiation dose RV1 (weighting of 100) correspondingto the deepest layer TVd, and the total irradiation dose becomes RV1.Each of, in total, three irradiations of the irradiation sequences 2, 11and 16 to the second layer is performed with a dose of ⅓ of anirradiation dose RV2 (weighting of 30) necessary for the second layer,and the total irradiation dose becomes RV2. Each of the irradiations ofthe irradiation sequences 3, 12 and 17 to the third layer is performedwith a dose of ½ of an irradiation dose RV3 (weighting of 28) necessaryfor the third layer, and the total irradiation dose becomes RV3. Eachof, in total, two irradiations of the irradiation sequences 4 and 13 tothe fourth layer are performed with a dose of ½ of an irradiation doseRV4 (weighting of 22) necessary for the fourth layer, and the totalirradiation dose become RV4. Each of, in total, two irradiations of theirradiation sequences 5 and 14 to the fifth layer is performed with adose of ½ of an irradiation dose RV5 (weighting of 20) necessary for thefifth layer, and the total irradiation dose becomes RV5.

This embodiment 5 is characterized in that the reirradiation, the numberof times of which is proportional to the weight, is performed to thedeepest layer TVd, and the second layer, the third layer, the fourthlayer, and the fifth layer each having a weighting (relative value) of20 or more. Also in this embodiment 5, even if the irradiation target TVis displaced by the physiological activity such as breadth, theirradiation error to the deepest layer TVd, the second layer, the thirdlayer, the fourth layer, and the fifth layer each having a highirradiation dose can be reduced.

EMBODIMENT 6

Next, embodiment 6 of the invention will be described. Since a particlebeam irradiation apparatus used in the embodiment 6 is the same as thatexplained in the embodiment 1 or the embodiment 2, the embodiment 6 of aparticle beam irradiation method of the invention will be mainlydescribed also in the embodiment 6.

In this embodiment 6, a particle beam PB is irradiated in an irradiationprocedure shown in FIG. 15. This control procedure is also stored in thestorage device of the control calculator to control the whole apparatus.In FIG. 15, respective irradiation layers of from the deepest layer TVdto the second layer, the third layer, . . . , the ninth layer arearranged along the vertical column, and weightings (relative values) tothe irradiation layers, and next thereto, the sequence of irradiationsof the first, the second, . . . , the tenth are arranged in thehorizontal columns thereof. Irradiation sequences are written as 1, 2,3, . . . , 24 at intersection points of the respective irradiationlayers and the respective sequence of irradiations. The particle beam PBis performed in order of the irradiation sequences 1, 2, 3, . . . , 24.

In the irradiation procedure of FIG. 15, the first irradiation includesthe irradiation of the irradiation sequence 1 to the deepest layer TVdand the irradiations of the irradiation sequences 2, 3, 4, 5, 6, 7, 8and 9 to the respective layers of from the second layer to the ninthlayer. The second irradiation includes the irradiation of theirradiation sequence 10 to the deepest layer TVd, the irradiation of theirradiation sequence 19 to the second layer, the irradiation of theirradiation sequence 21 to the third layer, the irradiation of theirradiation sequence 23 to the fourth layer, and the irradiation of theirradiation sequence 24 to the fifth layer. The third irradiationincludes the irradiation of the irradiation sequence 11 to the deepestlayer TVd, and the irradiations of the irradiation sequences 20 and 22to the second layer and the third layer. The fourth to the tenthirradiations are respectively the irradiations of the irradiationsequences 12 to 24 to the deepest layer TVd.

All the nine irradiations of the irradiation sequences 10 to 18 arereirradiations to the deepest layer TVd, the two irradiations of theirradiation sequences 19 and 20 are reirradiations to the second layer,and the irradiations of the irradiation sequences 21 and 22 arereirradiations to the third layer. The irradiations of the irradiationsequences 23 and 24 are respectively reirradiations to the fourth layerand the fifth layer. The nine reirradiations of the irradiationsequences of 10 to 18 to the deepest layer TVd are first collectivelyperformed, and subsequently to this, the reirradiations of theirradiation sequences 19 and 20 to the second layer are performed.Thereafter, the reirradiations to the third layer, the fourth layer, andthe fifth layer are executed.

Each of, in total, ten irradiations of the irradiation sequences 1 and10 to 18 to the deepest layer TVd are performed with a dose of 1/10 of ahighest irradiation dose RV1 (weighting of 100) corresponding to thedeepest layer TVd, and the total irradiation dose becomes RV1. Each of,in total, three irradiations of the irradiation sequences 2, 19 and 20to the second layer is performed with a dose of ⅓ of an irradiation doseRV2 (weighting of 30) necessary for the second layer, and the totalirradiation dose becomes RV2. Each of, in total, three irradiations ofthe irradiation sequences 3, 21 and 22 to the third layer is performedwith a dose of ⅓ of an irradiation dose RV3 (weighting of 28) necessaryfor the third layer, and the total irradiation dose becomes RV3. Eachof, in total, two irradiations of the irradiation sequences 4 and 23 tothe fourth layer is performed with a dose of ½ of an irradiation doseRV4 (weighting of 22) necessary for the fourth layer, and the totalirradiation dose becomes RV4. Each of, in total, two irradiations of theirradiation sequences 5 and 24 to the fifth layer is performed with adose of ½ of an irradiation dose RV5 (weighting of 20) necessary for thefifth layer, and the total irradiation dose becomes RV5.

This embodiment 6 is characterized in that with respect to the deepestlayer TVd, and the second layer, the third layer, the fourth layer, andthe fifth layer each having a weighting (relative value) of 20 or more,the reirradiation, the number of times of which is proportional to theweighting, is performed. Also in this embodiment 6, even if theirradiation target TV is displaced by the physiological activity such asbreath, the irradiation error to the deepest layer TVd, the secondlayer, the third layer, the fourth layer, and the fifth layer eachhaving the high irradiation dose can be reduced.

EMBODIMENT 7

Next, embodiment 7 of the invention will be described. In thisembodiment 7, the embodiment 7 of a particle beam irradiation apparatusof the invention and the embodiment 7 of a particle beam irradiationmethod of the invention will be described.

In this embodiment 7, a function is added in which breath measurement ofa patient or position detection of an irradiation target is performed,and based on the breath measurement or the position detection of theirradiation target, a breath judgment of the patient is performed, andturning on/off of irradiation of a particle beam PB is controlled.

In this embodiment 7, the particle beam irradiation apparatus of theembodiment 7 shown in FIG. 16 is used. The particle beam irradiationapparatus shown in FIG. 16 includes, in addition to a particle beamgeneration part 10, a particle beam transport part 20 and a particlebeam irradiation part 30, a breath measurement device 71, an irradiationtarget position detection device 73, a breath judgment calculator 75,and a particle beam treatment safety system 77. The particle beamgeneration part 10 and the particle beam transport part 20 are the sameas those shown in FIG. 4. The particle beam irradiation part 30 includesthe particle beam irradiation parts 30A, 30B and 30C of FIG. 4, and asits irradiation nozzle 31, the irradiation nozzle 31A used in theembodiment 1 shown in FIG. 5, or the irradiation nozzle 31B used in theembodiment 2 shown in FIG. 9 is used. In the particle beam irradiationmethod of the embodiment 7, the irradiation method described in theembodiment 1 to the embodiment 6 is used, and further, the turningon/off of the particle beam PB is controlled. Incidentally, in FIG. 16,a patient 70 is illustrated on a treatment stand 32. The particle beamirradiation part 30 irradiates the particle beam PB from just above thepatient 70.

The breath measurement device 71 measures the breath of the patient 70and outputs a breath signal BS, and what is used in a conventionalparticle beam treatment apparatus or an X-ray CT can be used. As thebreath measurement device 71, it is possible to use a unit in which alight-emitting diode (LED) is attached to the abdominal region or thechest region of the patient 70 and the breath is measured by thedisplacement of the light emitting position of the light emitting diode,a unit in which a reflecting device is used and the displacement of thebody is measured by a laser beam, a unit in which an extensible resistoris attached to the abdominal region of the patient and a change of theelectric characteristics is measured, a unit in which the breath of thepatient 70 is directly measured, or the like.

The irradiation target position detection device 73 detects the positionof the irradiation target TV in the patient 70 and outputs a breathsignal BS. As the irradiation target position detection device 73, X-raysources 731 and 732, and X-ray image acquisition devices 741 and 742corresponding to these are used. The X-ray sources 731 and 732 irradiateX-rays to the irradiation target TV in the patient 70, and the X-rayimage acquisition devices 741 and 742 acquire images of X-rays from theX-ray sources 731 and 732, and detects the position of the irradiationtarget TV. As the X-ray image acquisition devices 741 and 742, forexample, an X-ray television apparatus using an image intensifier, meansfor measuring a scintillator plate by a CCD camera, or the like is used.With respect to the irradiation target TV, there is a method of buryinga small piece of metal, such as gold, as a marker, and it becomes easyto specify the position of the irradiation target TV by using thismarker.

Both the breath measurement device 71 and the irradiation targetposition detection device 73 detects the displacement of the irradiationtarget TV due to the breath, and generates the breath signals BS. Boththe breath signals BS are inputted to the breath judgment calculator 75.The breath judgment calculator 75 judges, based on the correlation ofexhalation/inspiration stored in its storage means, the phase of abreath period in real time from the inputted breath signals BS, andoutputs a status signal SS to the particle beam treatment safety system77. The particle beam treatment safety system 77 supplies controlsignals CS to the particle beam generation part 10 and the particle beamtransport part 20 based on the status signal SS, and performs theturning on/off of the particle beam PB from the particle beamirradiation nozzle 31.

According to the embodiment 7, in synchronization with the breath, theturning on/off of the particle beam PB explained in the embodiment 1 tothe embodiment 6 is controlled, and the particle beam irradiation can beperformed with higher safety and high accuracy. Incidentally, one of thebreath measurement device 71 and the irradiation target positiondetection device 73 can be used.

EMBODIMENT 8

Next, embodiment 8 of the invention will be described. In thisembodiment 8, the embodiment 8 of a particle beam irradiation apparatusof the invention and the embodiment 8 of a particle beam irradiationmethod of the invention will be described.

In this embodiment 8, a function is added in which breath measurement ofa patient or position detection of an irradiation target is performed, abreath judgment of the patient is made based on the breath measurementor the position detection of the irradiation target, and turning on/offof a particle beam PB is controlled. This embodiment 8 is such that theparticle beam treatment safety system 77 in the embodiment 7 is replacedby an irradiation control calculator 80, and an irradiation dose of theirradiated particle beam PB is controlled based on a breath signal BS.The other structure is the same as the embodiment 7.

In this embodiment 8, the particle beam irradiation apparatus of theembodiment 8 shown in FIG. 17 is used. A particle beam generation part10 and a particle beam transport part 20 shown in FIG. 17 are the sameas those shown in FIG. 4. A particle beam irradiation part 30 includesthe particle beam irradiation parts 30A, 30B and 30C of FIG. 4. Theparticle beam irradiation part 30 includes an irradiation nozzle 31. Asthe irradiation nozzle 31, the irradiation nozzle 31A used in theembodiment 1 shown in FIG. 5, and the irradiation nozzle 31B used in theembodiment 2 shown in FIG. 9 are used. In the particle beam irradiationmethod of this embodiment 9, in addition to the irradiation methoddescribed in the embodiment 1 to the embodiment 7, control of theirradiation dose of the particle beam PB is performed.

In this embodiment 8, the breath phase of a patient 70 and the positionof the irradiation target TV corresponding thereto are measured, and thecorrelation of those is stored in storage means of a breath judgmentcalculator 75. The breath judgment calculator 75 receives a breathsignal BS from one of or both of a breath measurement device 71 and anirradiation target position detection part 73, and outputs in real timea position signal PS to indicate the position of the irradiation targetTV corresponding to the breath signal BS.

The irradiation control calculator 80 supplies an irradiation dosecontrol signal RS to indicate an irradiation dose corresponding to theposition signal PS to the particle beam irradiation part 30 based on theposition signal PS from the breath judgment calculator 75. The particlebeam irradiation part 30 adjusts the irradiation dose corresponding tothe irradiation target TV based on the position signal PS correspondingto the breath signal BS. For example, in the case where the irradiationtarget TV is the liver, in case the liver is displaced to move away fromthe irradiation nozzle 31 to a deep position by 1 cm at a certain phaseof breath, the irradiation dose of the particle beam PB is adjusted sothat the planned irradiation dose is obtained at this deep position. Theirradiation control calculator 80 can also be made the controlcalculator to control the whole apparatus explained in the embodiment 1to the embodiment 6.

In this embodiment 8, correspondingly to the displacement of theirradiation target TV due to the breath, the irradiation dose of theparticle beam PB explained in the embodiments 1 to 6 is adjusted, andtherefore, the irradiation with higher accuracy can be performed.Incidentally, in the embodiment 8, when the breath signal BS from theirradiation target position detection device 73 is used, as comparedwith the breath signal BS from the breath measurement device 71, theposition of the irradiation target TV can be more directly detected, andthe irradiation with higher accuracy can be performed.

EMBODIMENT 9

Next, embodiment 9 of the invention will be described. In thisembodiment 9, the embodiment 9 of a particle beam irradiation apparatusof the invention and the embodiment 9 of a particle beam irradiationmethod of the invention will be described.

Although an irradiation target TV of a patient 70 is displaced accordingto the breath of the patient 70, the displacement is mainly thedisplacement along a specific axis. With respect to an organ of thechest region and the abdominal region, there are many displacementsalong the lengthwise direction of the body by the operation of thediaphragm. FIG. 18 shows a state in which the irradiation target TV inthe patient 70 is displaced in an arrow C direction along the lengthwisedirection of the body.

Although the particle beam PB is irradiated as indicated by an arrow B1from just above the body in general, when the particle beam PB isirradiated as indicated by an arrow B2 from obliquely above a head 70 hof the patient 70, the displacement of the irradiation target TV in thearrow C direction by the breath of the patient 70 can be decomposed intothe irradiation direction of the particle beam PB, that is, the depthdirection and the lateral direction perpendicular thereto, and theirradiation error to the irradiation target TV by the breath can be madesmall.

In the embodiment 9, attention is paid to this, and the particle beam PBexplained in the embodiment 1 to the embodiment 6 is irradiatedobliquely with respect to the lengthwise direction of the body. In theparticle beam irradiation apparatus of the embodiment 9, both a rotationgantry 90 shown in FIGS. 19 and 20 and a treatment stand rotationmechanism are used.

The rotation gantry 90 is a large cylinder and is rotatable around ahorizontal axial line 91. A treatment stand 32 is installed inside therotation gantry 90. The treatment stand 32 is rotated by the treatmentstand rotation mechanism around a vertical axial line 92 perpendicularto the horizontal axial line 91. The particle beam irradiation nozzle 31is installed at an irradiation point P on the peripheral surface of therotation gantry 90.

FIG. 19 shows a state in which the horizontal axial line 91 and thelengthwise direction of the body become parallel to each other, and theparticle beam PB is irradiated just downward from the irradiation pointP in an arrow B1 direction. FIG. 20 shows a state in which the rotationgantry 90 is rotated by almost 45 degrees in the counterclockwisedirection from FIG. 19 around the horizontal axial line 91, and thetreatment stand 32 is rotated by 90 degrees around the vertical axialline 92 from FIG. 19. In the state of FIG. 20, the particle beam PB isirradiated along an arrow B2 obliquely from above the head 70 h of thepatient 70.

In the particle beam irradiation method of the embodiment 9, since theparticle beam PB is irradiated along the arrow B2 obliquely from abovethe head 70 h of the patient 70, the displacement of the irradiationtarget TV in the arrow C direction by the breath of the patient 70 canbe decomposed into the irradiation direction of the particle beam PB,that is, the depth direction and the lateral direction perpendicularthereto, and the irradiation error to the irradiation target TV by thebreath can be made small.

INDUSTRIAL APPLICABILITY

The irradiation method of the particle beam of the invention is used asthe treatment method for, for example, cancer or the like, and theirradiation apparatus of the particle beam of the invention is used asthe treatment apparatus for, for example, cancer or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] A diagram showing dose distributions of various radiation beamsin a body.

[FIG. 2] An explanation view showing conversion of irradiation energy bya bolus.

[FIG. 3] A dose distribution view of a particle beam in a body and in adepth direction.

[FIG. 4] A whole structural view of embodiment 1 of a particle beamirradiation apparatus of the invention.

[FIG. 5] An inner structural view of an irradiation nozzle of embodiment1.

[FIG. 6] An explanatory view of a particle beam irradiation method ofembodiment 1, in which FIG. 6( a) is a perspective view showing anirradiation target, and FIG. 6( b) is a scanning explanatory view ofirradiation spots.

[FIG. 7] An explanatory view of a conventional spot scanning technique,in which FIG. 7( a) is a perspective view showing an irradiation target,and FIG. 7( b) is a scanning explanatory view of irradiation spots.

[FIG. 8] A sectional view of a bolus used in the particle beamirradiation method of FIG. 6.

[FIG. 9] An inner structural view of an irradiation nozzle in embodiment2 of a particle beam irradiation apparatus of the invention.

[FIG. 10] A view showing an irradiation procedure in embodiment 2 of aparticle beam irradiation method of the invention.

[FIG. 11] A diagram showing an effect of the irradiation procedure ofembodiment 2.

[FIG. 12] A view showing an irradiation procedure in embodiment 3 of aparticle beam irradiation method of the invention.

[FIG. 13] A view showing an irradiation procedure in embodiment 4 of aparticle beam irradiation method of the invention.

[FIG. 14] A view showing an irradiation procedure in embodiment 5 of aparticle beam irradiation method of the invention.

[FIG. 15] A view showing an irradiation procedure in embodiment 6 of aparticle beam irradiation method of the invention.

[FIG. 16] A structural view of embodiment 7 of a particle beamirradiation apparatus of the invention.

[FIG. 17] A structural view of embodiment 8 of a particle beamirradiation apparatus of the invention.

[FIG. 18] An explanatory view of an irradiation direction of a particlebeam relating to embodiment 9 of a particle beam irradiation method ofthe invention.

[FIG. 19] A perspective view showing embodiment 9 of a particle beamirradiation apparatus of the invention.

[FIG. 20] A perspective view showing a rotation state of embodiment 9 ofthe particle beam irradiation apparatus of the invention.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

10: particle beam generation part, 12: accelerator, 15, 60: depthdirection irradiation field spread means, 20: particle beam transportpart, 30, 30A, 30B, 30C: particle beam irradiation part, 31, 31A, 31B:irradiation nozzle, 40: lateral direction irradiation field spreadmeans, TV: irradiation target, TVd: deepest layer, S: irradiation spot,PB: particle beam, 45: bolus, 50: lateral direction irradiation fieldspread means, 71: breath measurement device, 73: irradiation targetposition detection device, 75: breath judgment calculator, 77: particlebeam treatment device safety system, 80: irradiation control calculator,90: rotation gantry.

1. A particle beam irradiation method which uses both a depth directionirradiation field spread for spreading an irradiation field of aparticle beam in a depth direction along an irradiation direction of theparticle beam, and a lateral direction irradiation field spread forspreading the irradiation field of the particle beam in a lateraldirection perpendicular to the irradiation direction of the particlebeam, and which irradiates the particle beam on an irradiation target,wherein the depth direction irradiation field spread is an activeirradiation field spread in which plural irradiation layers havingdifferent ranges in the irradiation direction of the particle beam aresuperimposed, the lateral direction irradiation field spread is anactive irradiation spread in which irradiation spots of the particlebeam are superimposed in the lateral direction, and a bolus having ashape along a deepest part of the irradiation target in the depthdirection is disposed to cross the particle beam.
 2. The particle beamirradiation method according to claim 1, wherein at least oneirradiation layer selected from the plural irradiation layers isre-irradiated once or more with the particle beam.
 3. The particle beamirradiation method according to claim 2, wherein the selectedirradiation layer is made an irradiation layer having a highestirradiation dose in the plural irradiation layers, and the selectedirradiation layer is re-irradiated once or more with the particle beam.4. The particle beam irradiation method according to claim 2, whereinplural selected irradiation layers are selected from the pluralirradiation layers, and each of the plural selected irradiation layersis re-irradiated once or more with the particle beam.
 5. The particlebeam irradiation method according to claim 4, wherein the number oftimes of reirradiation of each of the plural selected irradiation layerscorresponds to a planned irradiation dose for each of the selectedirradiation layers.
 6. The particle beam irradiation method according toclaim 1, wherein a displacement of the irradiation target is detected,and turning on/off of irradiation of the particle beam is performedaccording to the displacement of the irradiation target.
 7. The particlebeam irradiation method according to claim 1, wherein a displacement ofthe irradiation target is detected, and an irradiation dose of theparticle beam is controlled according to the displacement of theirradiation target.
 8. The particle beam irradiation method according toclaim 1, wherein in a case where the irradiation target is displacedmainly along a specified direction, the particle beam is irradiated tothe irradiation target from a direction oblique to the specifieddirection.
 9. A particle beam irradiation apparatus comprising: aparticle beam generation part for generating a particle beam; a particlebeam transport part for transporting the particle beam generated by theparticle beam generation part; a particle beam irradiation part forirradiating the particle beam transported by the particle beam transportpart to an irradiation target; depth direction irradiation field spreadmeans for spreading an irradiation field of the particle beam in a depthdirection along an irradiation direction of an irradiation direction ofthe particle beam; and lateral direction irradiation field spread meansfor spreading the irradiation field of the particle beam in a lateraldirection perpendicular to the irradiation direction of the particlebeam, wherein the depth direction irradiation field spread means is anactive depth direction irradiation field spread means for superimposingplural irradiation layers having different ranges in the irradiationdirection of the particle beam, the lateral direction irradiation fieldspread means is an active irradiation field spread means forsuperimposing irradiation spots of the particle beam in the lateraldirection, and a bolus having a shape along a deepest part of theirradiation target in the depth direction is disposed to cross theparticle beam.
 10. The particle beam irradiation apparatus according toclaim 9, wherein the active depth direction irradiation field spreadmeans is coupled to an accelerator for accelerating the particle beam,and changes its acceleration energy.
 11. The particle beam irradiationapparatus according to claim 9, wherein the active depth directionirradiation field spread means is a range shifter disposed to cross theparticle beam, and the range shifter adjusts energy of the particle beamaccording to a given adjustment signal.
 12. The particle beamirradiation apparatus according to claim 9, wherein the particle beamirradiation apparatus further comprises displacement detection means fordetecting a displacement of the irradiation target, and turning on/offmeans for turning on/off irradiation of the particle beam, and theparticle beam is turned on/off according to the displacement of theirradiation target.
 13. The particle beam irradiation apparatusaccording to claim 9, wherein the particle beam irradiation apparatusfurther comprises displacement detection means for detecting adisplacement of the irradiation target, and adjustment means foradjusting an irradiation dose of the particle beam, and the irradiationdose of the particle beam is adjusted according to the displacement ofthe irradiation target.
 14. The particle beam irradiation apparatusaccording to claim 9, wherein the particle beam irradiation partincludes an irradiation nozzle for irradiating the particle beam, theirradiation nozzle is mounted on a rotation gantry, and in a case wherethe irradiation target is displaced mainly along a specified direction,the particle beam is irradiated to the irradiation target from adirection oblique to the specified direction.